Condenser
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a heat exchanger, more particularly, to a condenser suitable for use in an automotive air conditioning system. 
     2. Description of the Prior Art 
     Japanese Utility Model Application Publication No. 58-104867 discloses a condenser suitable for use in an automotive air conditioning system. With reference to FIG. 1 of this first prior art device, the condenser includes serpentine-shaped flat pipe 110 for conducting a refrigerant therethrough. Serpentined flat pipe 110 comprises a plurality of straight portions 110a located parallel to each other. Straight portions 110a fixedly sandwich corrugated fins 111 therebetween. Inlet and outlet unions 112 and 113 are fixedly and hermetically connected at both open ends of serpentined flat pipe 110 respectively. 
     In this first prior art device, reduction of the gap H&#39; between straight portions 110a is restricted because the flat pipe 110 must be bent into the serpentine shape, thereby limiting to elevation of heat radiating efficiency of fin 111. Further, a high flow resistance is encountered when the refrigerant flows through flat pipe 110, because the refrigerant must flow through each straight position 110a in series from the inlet to the exit union. Finally, this structure is thereby limited by the gap H&#39;, i.e., distance between flat pipes and is further limited by the heat radiating efficiency of fins 111. 
     To overcome the above-mentioned defects, Japanese Patent Application Publication No. 63-112065 discloses a second prior art device. With reference to FIG. 2, the condenser includes a plurality of flat pipes 120 of aluminum alloy located parallel to each other. Each flat pipe 120 conducts refrigerant therethrough. Flat pipes 120 fixedly sandwich corrugated fins 121 of clad aluminum alloy therebetween. 
     First header pipe 122 having an open end and a closed end is mounted perpendicular to flat pipes 120 and is fixedly and hermetically connected to one end of each flat pipe 120. Inlet union 122a is fixedly and hermetically connected to the open end of first header pipe 122. Second header pipe 123, also having an open end and a closed end, is mounted perpendicular to flat pipes 120 and is fixedly and hermetically connected to the other end of each flat pipe 120. Outlet union 123a is fixedly and hermetically connected to the open end of second header pipe 123. 
     In the construction of the second prior art device, the refrigerant in first header pipe 122 first flows into inlet union 122a, then distributively flows into each flat pipe 120, and sequentially flows together into second header pipe 123, so that the flow resistance generated as the refrigerant flows through flat pipe 120 is remarkably less than the flow resistance in the first prior art device. Accordingly, the diameter of the flat pipes 120 can be reduced without generating high flow resistance. Consequently, the number of flat pipes 120 can be increased without increasing the size of the condenser, that is, the gap H in the second prior art device is less than the gap H&#39; in the first prior art device. As a result, a condenser having a greater ability to exchange heat is obtained. 
     In the second prior art device, inlet and outlet unions 122a, 123a are fixedly and hermetically connected to each open end of first and second header pipes 122 and 123 respectively, for example, by brazing. That is, two hermetically joined portions between the union and the header pipe exist. 
     However, it is desirable to provide only one union element to the header pipes, because the number of potentially defective hermetically joined portions is proportional to the number of hermetically joined portions. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to reduce the fraction of defective union element/header pipe junctions by reducing the number of union element/header pipe junctions. 
     It is another object of the present invention to reduce the number of parts of the condenser, thereby decreasing the manufacturing cost. 
     The present invention is directed toward providing these objectives with a condenser which preferably includes a plurality of flat metal tubes for conducting fluid having opposite first and second ends respectively. A plurality of metal fins are sandwiched by the flat metal tubes. First and second header pipes, which are closed at both ends respectively, are fixedly and hermetically mounted on the opposite ends of the flat metal tubes respectively, so that the flat metal tubes communicate with the interior of each header pipe. An inlet union element hermetically connects the condenser to an upstream element with respect to the condenser, for example, a compressor. An outlet union element hermetically connects the condenser to a downstream element with respect to the condenser, for example, a receiver drier. A member including the inlet and outlet union elements in one body is preferably fixedly and hermetically connected to the longitudinal center of one of the first and second header pipes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the invention becomes better understood from the following detailed description with reference to the attached drawings. 
     FIG. 1 is a front elevation view of a condenser in accordance with the first prior art device. 
     FIG. 2 is a front elevation view of a condenser in accordance with the second prior art device. 
     FIG. 3 is a front elevation view of a condenser in accordance with the preferred embodiment of the present invention. 
     FIG. 4 is an enlarged fragmentary vertical sectional view of the condenser shown in FIG. 3. 
     FIG. 5 is a front elevation view of an essential part of a condenser in accordance with a second embodiment of the present invention. 
     FIG. 6 is a plan view of the essential part of the condenser shown in FIG. 5. 
     FIG. 7 is a vertical sectional view of the essential part of the condenser shown in FIG. 5. 
     FIG. 8 is a front elevation view of an essential part of a condenser in accordance with a third embodiment of the present invention. 
     FIG. 9 is a plan view of the essential part of the condenser shown in FIG. 8. 
     FIG. 10 is a vertical sectional view of the essential part of the condenser shown in FIG. 8. 
     FIG. 11 is a transverse sectional view of the essential part of the condenser shown in FIG. 8. 
     FIG. 12 is a plan view of an essential part of a condenser in accordance with a fourth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A condenser in accordance with the preferred embodiment of the present invention is shown in FIG. 3. In the drawing, the same numerals are used to denote the corresponding elements shown in FIG. 2 and in such cases an explanation thereof is omitted. 
     First header pipe 132, having both ends closed, is made of clad aluminum alloy. First header pipe 132 is mounted perpendicular to flat pipes 120 and is fixedly and hermetically connected to one end of each flat pipe 120 by brazing. Second header pipe 133 has both ends closed and is made of a clad aluminum alloy. Second header pipe 133 is also mounted perpendicular to each flat pipe 120 and is fixedly and hermetically connected to the other end of each flat pipe 120 by brazing. The horizontal axis X of the condenser is preferably parallel to the longitudinal axes of the flat pipes 120. The vertical axis Y of the condenser is preferably parallel to the longitudinal axes of the header pipes 132, 133 and preferably perpendicular to the longitudinal axes of the flat pipes 120. 
     Referring to FIG. 4, the preferred union element 10 comprises inlet portion 101 having a longitudinal axis L, outlet portion 102 having a longitudinal axis M, and main body portion 103 which are integrally formed together. Main body portion 103 is aligned perpendicularly to first header pipe 132 and is fixedly and hermetically connected by brazing to the edge of opening 132a, which is in the longitudinally central portion of first header pipe 132. Inlet and outlet portions 101, 102 are located opposite to each other and both are aligned parallel to first header pipe 132. 
     Each of inlet and outlet portions 101, 102 includes a hexagonal nut portions 101b, 102b respectively, formed at the basal part thereof and outside threaded portions 101a, 102a respectively, formed at a remainder thereof. 
     Large cavity 105, which is communicatingly connected to the interior of first header pipe 132 through opening 132a, is formed in main body portion 103. Holes 106, 107 extending from cavity 105 are axially bored through inlet and outlet portions 101, 102 respectively and are open at each axial end of inlet and outlet portions 101, 102. 
     Wall 104 partitions cavity 105 into first cavity 105a from which hole 106 extends and second cavity 105b from which hole 107 extends. Wall 104 further projects toward an inner arcuate surface (to the left in FIG. 4) of first header pipe 132, and is hermetically connected thereto by brazing, thereby hermetically dividing the inside space of first header pipe 132 into upper space portion 132b and lower space portion 132c. Accordingly, first and second cavities 105a, 105b are hermetically linked to upper and lower space portions 132b, 132c respectively. 
     In the above construction, when the automotive air conditioning system is operated, refrigerant gas from a compressor (not shown) flows into hole 106 through a pipe member (not shown). Consequently, the refrigerant gas distributively flows through each flat pipe 120 located in the upper half portion of the condenser via first cavity 105a  and upper space portion 132b, then flows together in second header pipe 133. When the refrigerant gas flows through flat pipes 120 located in the upper half portion of the condenser, the refrigerant gas exchanges heat with the air outside the condenser. That is, it radiates heat to the outside air and is condensed. 
     Refrigerant flowing together in second header pipe 133 then distributively flows from each flat pipe 120 located in the lower half portion of the condenser. With heat exchanging causing the refrigerant to be liquefied, consequently, the refrigerant flows out to a receiver drier (not shown) through a pipe member (not shown) via lower portion 132c, second cavity 105b and hole 107. 
     FIGS. 5, 6 and 7 illustrate a second embodiment of the present invention. In this embodiment, inlet portion 101 having longitudinal axis L is aligned parallel to first header pipe 132. Outlet portion 102 having longitudinal axis M is perpendicular to inlet portion 101 and is opposite to flat pipe 120. 
     FIGS. 8, 9, 10 and 11 illustrate a third embodiment of the present invention. In this embodiment, inlet portion 101 having longitudinal axis L is opposite to flat pipe 120. Outlet portion 102 having a longitudinal axis M is perpendicular to both inlet portion 101 and first header pipe 132. 
     The position of each inlet and outlet portion 101, 102 is not restricted to the above-mentioned embodiments. Other varied positions for each inlet and outlet portion 101, 102 can still fall within the scope of the claimed invention. 
     FIG. 12 illustrates a fourth embodiment of the present invention. In this embodiment, first header pipe 132&#39; is square, while the first header pipe in the first, second and third embodiments of the present invention is round. 
     This invention has been described in detail in connection with the preferred embodiment and alternative embodiments. These embodiments, however, are merely for example only and the invention is not restricted thereto. It will be understood by those skilled in the art that other variations and modifications can easily be made within the scope of this invention as defined by the claims.